This invention relates generally to sheet holding tray cassettes for photocopy machines and particularly to trays insertable into tray receiving assemblies mounted in photocopiers.
Many photocopy machines provide for paper to be supplied to the machine from removable trays. The trays are filled outside the machine and are then inserted into the machine where they are engaged by or engageable with feeding elements. The feeding elements must ordinarily be disengaged from the tray to allow unhindered removal of the tray, and should be clear of the tray when the tray is reinserted, to prevent damage to the feed apparatus.
In addition, when the tray is in its operative position, wherein the feed mechanism can feed sheets one at a time, removal of the tray could cause severe damage to the feed system. In particular, in those feed systems in which an operating feed system member passes through at least one wall of the tray (as, for example, in the copier sold by Nashua Corporation, Nashua, N.H., under the designation 1220 Copier) both the tray and the machine can be damaged if the tray is removed and/or inserted when that tray is selected.
After a tray is inserted, it is important that the feed rollers engage the stack of paper properly. The rollers are often in pairs, to engage the paper on opposite sides of a center feed line, and it is desirable to have each roller engage the sheet stack firmly with equal pressure. Due to normal manufacturing tolerances, both feed rollers might not engage the paper firmly unless some compensation for "misalignment" is made. One compensation used has been to have the ramp plate in the tray, on which the paper is stacked, freely pivotable about the center, inward of its rear edge. This can be accomplished by creating a downwardly projecting dimple inward from the rear edge of the ramp plate, about which pivoting can be accomplished (as in the Nashua 1220 Copier, referred to earlier).
It is therefore an object of this invention to provide a tray and tray receiving assembly that provides for positive locking of the tray in its operative position to prevent damage to the tray or feed elements by improper removal of the tray from the machine. It is another object to provide for supporting the paper supporting plate to provide a sheet stack that is automatically aligned with the photocopier feed rollers. Other objects are to provide a reliable, positive acting, tray and tray receiving assembly that is efficient and inexpensive to manufacture and maintain.